The correct answer is y=28 cm 
Explain 
Area of 4  congruent  parallelograms= 308cm^2 
Area of 1 parallelogram = 308/ 4
Area of 1 parallelogram = 77 cm ^2 
h+h= 14 
As h+h=2h 
2h=14
Divide both side by by 2 
H= 7 
Solve for b 
As b+b = 2b 
2b+6=y
Subtract both side by  6 
2b+6-6=y-6
Combining numbers 
2b=y-6
Divide both side by 2 
2b/2 = y-6/2 
Cancel 2 
B= y-6/2 
We have of 1 parallelogram = 77 cm^2 
H= 7 
B= y-6/2 
Parallelogram area = bh 
So now parallelogram area = y-6/2 x7 
And area of 1 parallelogram = 77 cm^2
Y-6/ 2 x 7 = 77 
Y-6/2  x 7= 7(11) 
Cancel 7 
Y-6/2 = 11 
Multiple both by 2 
2(y-6/ 2) = 11x2 
Cancel 2  and multiple numbers 
Y-6=22
Add  6  both sides 
Y-6+6=22+6
Y=28